The present invention relates to navigation satellite receivers, and more particularly to methods and systems for worldwide sharing of GPS reference stations over a network server.
Global positioning system (GPS) receivers use signals received from several earth-orbiting satellites in a constellation to determine user position and velocity, and other navigational data. A navigation receiver that has just been turned on does not yet know where it is, how much its crystal oscillator is in error, nor what time it is. All these are needed to find and lock onto the satellite transmissions, and so a search must be made of all the possibilities.
Each GPS satellite vehicle (SV) transmits navigation (NAV) data at fifty bits-per-second, and includes ephemeris, clock and almanac information. Such information allows a GPS receiver to compute its position, velocity, and time. One whole data frame of NAV data is 1500-bits long, and thus takes thirty seconds to transmit.
It is therefore an object of the present invention to provide a method and system for gathering and sharing information that can assist navigation satellite reception and receiver initialization.
It is another object of the present invention to provide a method and system for reducing the cost and duplication of GPS reference stations and servers distributed throughout the world.
It is a further object of the present invention to provide a satellite-navigation system that is cost effective.
Briefly, a reference station system embodiment of the present invention comprises-a plurality of GPS reference stations that are distributed in different parts of the world to be able to simultaneously gather a complete set of satellite vehicle ephemeredes. Each reference station is associated with a network server connected to the Internet. Each network server posts ephemeredes, NAV-data, and other useful information for clients derived from its corresponding reference station. All such network servers inject their information in all the other servers in the system Each server validates and authenticates any injected data. Each client is also qualified as a subscriber before being able to access the complete ephemeredes database and other GPS system information.
An advantage of the present invention is that a system and method are provided that allows single clients to subscribe to one reference station server no matter where they travel.
Another advantage of the present invention is that a system and method are provided for making simple and cost effective navigation satellite reference stations and servers.